1. Field
A linear compressor is disclosed herein.
2. Background
In general, compressors may be mechanisms that receive power from power generation devices, such as electric motors or turbines, to compress air, refrigerants, or other working gases, thereby increasing a pressure of the working gas. Compressors are widely used in home appliances or industrial machineries, such as refrigerators and air-conditioners.
Compressors may be largely classified into reciprocating compressors, in which a compression space, into and from which a working gas, such as a refrigerant, is suctioned and discharged, is defined between a piston and a cylinder to compress the refrigerant while the piston is linearly reciprocated within the cylinder; rotary compressors in which a compression space, into and from which a working gas, such as a refrigerant, is suctioned and discharged, is defined between a roller that is eccentrically rotated and a cylinder to compress a refrigerant while the roller is eccentrically rotated along an inner wall of the cylinder; and scroll compressors, in which a compression space, into and from which a working gas, such as a refrigerant, is suctioned and discharged, is defined between an orbiting scroll and a fixed scroll to compress a refrigerant while the orbiting scroll is rotated along the fixed scroll. In recent years, among the reciprocating compressors, linear compressors having a simple structure in which the piston is directly connected to a drive motor, which is linearly reciprocated, to improve compression efficiency without mechanical loss due to switching in moving, are being actively developed. Generally, such a linear compressor is configured to suction and compress a refrigerant while a piston is linearly reciprocated within a cylinder by a linear motor in a sealed shell, thereby discharging the compressed refrigerant.
The linear motor has a structure in which a permanent magnet is disposed between an inner stator and an outer stator. The permanent magnet may be linearly reciprocated by a mutual electromagnetic force between the permanent magnet and the inner (or outer) stator. Also, as the permanent magnet is operated in a state in which the permanent magnet is connected to the piston, the refrigerant may be suctioned and compressed while the piston is linearly reciprocated within the cylinder and then be discharged.
FIGS. 1 and 2 illustrate a magnet assembly in a related art linear compressor. The magnet assembly 1 of FIGS. 1-2 includes a magnet frame 2 having an approximately cylindrical shape that delivers a drive force exerted by a linear motor to a piston, and a permanent magnet 3 fixed on an outer circumference of the magnet frame 2.
The magnet assembly 1 further includes a coupling plate 4 coupled to an end portion of the magnet frame 2. The coupling plate 4 may be disposed to cover an open end portion of the magnet frame 2.
The piston may be coupled to the coupling plate 4. In addition, the piston may be coupled to the coupling plate 4 and extend inside the magnet frame 2. When the linear motor is driven, the permanent magnet 3, the magnet frame 2, the coupling plate 4, and the piston may be integrally reciprocated.
On the outer circumference of the magnet frame 2, the permanent magnet 3, a plurality of supporting members 6 and 7 to support both sides of the permanent magnet 3, and a fixing member 5 that couples the permanent magnet 3 to the coupling plate 4 are provided. The plurality of supporting members 6 and 7 include a first supporting member 6 to support a first side of the permanent magnet 3 and a second supporting member 7 to support a second side.
The permanent magnet 3 is disposed between the first and second supporting members 6 and 7. In addition, the first supporting member 6 may be positioned between the permanent magnet 3 and a flange 4a of the coupling plate 4.
In more detail, the coupling plate 4 may have a bent shape to cover at least a portion of the outer circumference of the magnet frame 2 with the open end portion of the magnet frame 2 covered. The coupling plate 4 includes the flange 4a, which forms one end portion of the coupling plate 4 and which is separately disposed from the permanent magnet 3 or the first supporting member 6. The fixing member 5 is configured to cover the first supporting member 6 and the flange 4a of the coupling plate 4.
The supporting member 5 includes a connection 5a coupled to the outer circumference of the magnet frame 2. The connection 5a may be a part of the fixing member 5 disposed between the permanent magnet 3 and the coupling plate 4.
The permanent magnet 3 may be made of a rare-earth magnet, for example, neodymium magnet or ND magnet. The ND magnets have very large magnetic flux density. In addition, as the coupling plate 4 is made of a magnetic material, the magnetic flux density generated from the ND magnets may leak outside through the coupling plate 4.
Accordingly, in order to prevent the magnetic flux generated by the ND magnet from leaking outside through the coupling plate 4, the permanent magnet 3 may be disposed a predetermined distance from the flange 4a of the coupling plate 4. In addition, as shown in FIG. 2, the connection 5a may be positioned such that the flange 4a is separated from the permanent magnet 3.
In such a way, in a case in which the coupling plate 4 is separately disposed from the permanent magnet 3 and the fixing member 5 is disposed between them, the fixing member 5 or the coupling plate 4 may be damaged in a process during which the permanent magnet 3 and the coupling plate 4 are reciprocated from side to side. In particular, in the process during which the permanent magnet 3 and the coupling plate 4 are reciprocated, compressive force and tensile force are applied to the connection 5a of the fixing member 5 and the action of the forces are repeated. Accordingly, a strength of the connection 5a becomes weakened, and accordingly, the connection 5a becomes damaged. When the connection 5a is damaged, the coupling plate 4 becomes also damaged due to interference between the permanent magnet 3 and the coupling plate 4.
Further, in order to address the above described limitations, proposals to reduce a size of the connection 5a, in particular, proposals to increase a length or a size of the permanent magnet 3 have been considered. However, ND magnets are very expensive and the proposals are very restrictive. In a case of reducing the size of the connection 5a by reducing a distance between the permanent magnet 3 and the coupling plate 4, a leaked amount of magnetic flux increases and then efficiency of the compressor is reduced.